The present embodiments relate to solid phase change ink compositions characterized by being solid at room temperature and molten at an elevated temperature at which the molten ink is applied to a substrate. These solid ink compositions can be used for ink jet printing in a variety of applications. The present embodiments are directed to curable solid inks (CSI) and low shrinkage curable solid inks (LS-CSI) and methods of using the inks. The solid inks of the present embodiments have a unique combination of characteristics, such as enhanced robustness, lower jetting temperature, and ultra-low shrinkage upon crystallization, that allow the inks to be used as novel materials in inkjet-based Braille and raised print applications.
Ink jet printing processes generally may employ inks that are solid at room temperature and liquid at elevated temperatures. Such inks may be referred to as solid inks, hot melt inks, phase change inks and the like. For example, U.S. Pat. No. 4,490,731, the disclosure of which is totally incorporated herein by reference, discloses an apparatus for dispensing solid ink for printing on a recording medium such as paper. In thermal ink jet printing processes employing hot melt inks, the solid ink is melted by the heater in the printing apparatus and utilized (jetted) as a liquid in a manner similar to that of conventional thermal ink jet printing. Upon contact with the printing recording medium, the molten ink solidifies rapidly, allowing the colorant to substantially remain on the surface of the recording medium instead of being carried into the recording medium (for example, paper) by capillary action, thereby enabling higher print density than is generally obtained with liquid inks. Advantages of a solid ink in ink jet printing are thus elimination of potential spillage of the ink during handling, a wide range of print density and quality, minimal paper cockle or distortion, and enablement of indefinite periods of nonprinting without the danger of nozzle clogging, even without capping the nozzles.
Solid inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in solid ink jet printers wherein the ink droplets are applied directly onto the final recording medium (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the recording medium, so that migration of ink along the printing medium is prevented and dot quality is improved.
While the above conventional solid ink technology is generally successful in producing vivid images and providing economy of jet use and substrate latitude on different substrates, such technology often does not meet the additional requirements for specialized applications such as Braille and raised print applications. There are two main technologies available for printing Braille and raised characters: embossing and thermal paper expansion. Neither is easily adapted to producing digital prints and a simple solution for digital generation of Braille and raised text is desired, particularly by government and large institutions which are required by law to provide Braille prints for visually impaired people. In addition, packaging converters are being increasingly asked and mandated, particularly in Canada and the European Union, to provide Braille printing on packages for the pharmaceutical industry. U.S. Patent Publication No. 2010/0053287, hereby incorporated by reference, previously demonstrated the use of solid inkjet printer with optional raised print capability. While raised prints could be obtained, however, the markings made with solid ink were insufficiently robust and thus required special handling.
As such, there is a need to overcome the deficiencies of conventional solid ink technology for these applications to better serve the market. Advantages of digitally producing Braille and raised text are personalization, accessibility to home users, ease of combination with regular text, and the ability to easily generate Braille representations of mathematical and chemical equations and financial formulae.
Each of the foregoing U.S. patents and patent Publications are incorporated by reference herein. Further, the appropriate components and process aspects of the each of the foregoing U.S. patents and patent Publications may be selected for the present disclosure in embodiments thereof.